A compressor of this kind has been disclosed in West German Offenlegungsschrift 3 314 705. This compressor transforms changes in the pressure inside the compression space of a Stirling engine into axial displacement of a diaphragm. The axial displacement produces pumping action, whereby the fluid inside the fluid circuit is compressed or circulated.
In this conventional compressor, only the pressure of the working gas inside the working space of the Stirling engine and the pressure of the fluid inside the fluid circuit act on the opposite sides of the diaphragm. Therefore, if the average pressures on both sides of the diaphragm differ, it is displaced toward the lower pressure side. This impedes axial displacement of the diaphragm if the pressure inside the compression space varies. Thus, no pumping action takes place. Furthermore, no Stirling cycle is created, because the changing pressure of the working space including the expansion space and the compression space is in phase with the axial displacement of the diaphragm. Hence, the output of the Stirling engine cannot be efficiently used in the compressor.